The invention relates to power transmission devices and, more particularly, to a device operable to maintain a desired preload on a bearing in an axle assembly.
It is known to rotatably support a differential case in an axle assembly housing using a pair of bearing assemblies. The bearing assemblies are typically constructed to have an inner race, an outer race and a plurality of rollers positioned between the inner race and the outer race. To achieve long bearing life during vehicle operation, it has been found that an axial preload positively affects bearing life.
Some axle assemblies include adjustment mechanisms operable to apply a desired preload to a bearing assembly. During axle assembly, an adjustment nut is typically rotated until a desired preload is met and then the adjustment nut is fixed at that rotational position. Alternately, portions of the axle housing may be separated by application of an external force while the differential assembly and bearings are installed within the axle housing. After installation of the bearings and differential assembly, the force applied to the axle housing is released to provide an axial load to the bearing assemblies.
While these methods have functioned well in the past to provide a desired bearing preload, improvements may be made. Specifically, a concern regarding maintaining the desired bearing preload exists when the axle assembly is constructed using a variety of materials having different coefficients of thermal expansion. Specifically, some axle assembly housings are created using aluminum while the differential case may be constructed from cast iron or steel. As the operating temperature of the axle assembly varies, specific components expand and contract at different rates. As such, the bearing preload set at a specific temperature varies as the temperature deviates from the initial build condition.